The present invention relates to a feed trough and to a method for transmitting HF or RF energy through the wall of a gas tight treatment chamber, in particular a vacuum chamber, and to a rotatable, at least partially electroconductive carrier for at least one workpiece to be treated, as well as to the use thereof and to a vacuum treatment plant with a vacuum chamber and a feed trough.
Various treatment methods are known wherein a workpiece to be treated is introduced into a treatment chamber which is gas tight with respect to the atmosphere and, in order to be treated uniformly depending on the treatment process considered, is moved in the chamber by rotating a workpiece carrier. In particular, a procedure is known for use during a vacuum treatment process in a vacuum chamber where, at least as part of the treatment process, a high-frequency gas discharge is involved, such as a high-frequency ion etching process, a high-frequency sputtering process or an HF substrate bias process, for example.
For such processes or partial processes a feed trough must be provided for applying the high-frequency energy to the electroconductive rotating carrier or to the electroconductive parts thereof, while maintaining vacuum tight conditions. In this connection it is known to apply the high-frequency energy through wiper contacts to a bearing shaft for the carrier, but this entails various disadvantages. If the shaft traverses the gas tight chamber envelope, i.e. generally the wall thereof, a dynamic gas seal, in particular a dynamic vacuum seal, must be provided there. The wiper contact can then be placed outside the chamber, so that abrasion, which is never completely avoidable, does not effect the conditions inside the chamber. However, the layout of a gas tight, especially a vacuum tight dynamic seal is then a problem if the shaft diameter is relatively large, i.e. a limit is set for the shaft dimension. On the other hand, if the wiper contact is provided inside the chamber, i.e. under the conditions prevailing therein, the abrasion referred to causes contamination in the treatment chamber, which in many cases cannot be tolerated. In addition, the electrical load of such a vacuum contact is restricted to much narrower limits due, for example, to the problem of cooling.
In principle, providing wiper contacts, whether lying inside or outside the chamber, is critical for the feeding of HF energy, especially when high energies must be transmitted.